Leonard Shapiro DMD, MS
Five years after placement, high survival rates can be expected for implants and implant-supported single crowns.
Based solely on retrospective and prospective studies with a short follow-up, this review provides moderate support for considering implant-supported single crowns as a viable treatment option for single missing teeth.
A) What is the 5-year survival rate of implant-supported single crowns? B) What is the incidence of biological and technical complications?
The authors conducted a comprehensive search of 1 electronic database (1966 to July 2006), manual searches of the bibliography and hand searches of several journals in both English and German. The search yielded a total of 26 articles, 21 prospective and 5 retrospective, respectively. Two independent reviewers screened the titles and abstracts and included studies that a) had a mean duration of follow-up of at least 5 years b) were published in English or German c) had clinical examination at follow-up d) reported details of the superstructure characteristics and; e) combined findings for implant supported FPD’s and single crowns but allowed data extraction for the single crowns group.
Survival of single crowns was defined as crowns remaining in situ with or without modifications. Biologic complications were defined as the disturbances to function of the implant due to biologic processes while technical complications were defined as mechanical damage to implants, implant components and/or supra-structures. The 26 studies compared a total of 1558 implants in patients ranging in age from 13 to 94 years. Drop-out rates varied from 0% to 30%. 11 of the 26 studies had variable individual patient observations periods ranging from 1 to 16 years. The 5-year survival rate of implants supporting single crowns was 96.8%. Based on thirteen studies, the authors reported a 5-year survival rate of 94.5% for single crowns supported by implants (n = 534). From 7 studies, they reported a 4.2% higher 5-year survival rate for metal ceramic crowns over all-ceramic crowns. None of these 7 studies actually performed a comparative study between the two materials.
Peri-implantitis was the most frequent biological complication that occurred in 9.7% of the implants. Marginal bone loss exceeding 2mm was seen in 6.3% of all implants cases. Reports of technical complications included screw loosening (12.7%), loss of retention (5.5%), fracture of veneer (4.5%) and rarely fracture of other components.
For implants supporting single crowns, a 5-year survival rate of 96.8% can be expected. For single crowns supported by implants, a 5-year survival rate of 94.5% can be expected. However, biologic and technical complications are frequent.
Source of Funding:
No source of funding was disclosed.
Importance and Context:
There are a number of therapeutic options for replacing a single missing tooth. These include conventional tooth supported bridges, cantilever bridges, resin-bonded bridges and implant-supported single crowns. The success of implant-supported crowns depends on factors such as design, placement technique, loading time and the patient's periodontal health.
Strengths and Weaknesses of the Systematic Review:
The authors performed a comprehensive search of only one electronic data base and did not state whether the inclusion criteria were established in advance of the search. The reviewers used accepted methods to select articles, but they inappropriately aggregated all studies instead of separately examining prospective and retrospective studies. They did not report a formal review of the validity of each study. Also, because the authors combined studies evaluating different implant systems and placement techniques, they may have introduced further heterogeneity into the results. Although the authors discussed reasons for a short follow-up of 5 years, the short follow-up remains an important weakness.
Strengths and Weaknesses of the Evidence:
In the absence of randomized controlled trials, this review was limited to lower levels of evidence from 21 prospective and 5 retrospective studies. These studies primarily were conducted in institutional and specialist settings. As a result, this could lead to an overestimate of success in a general practice. Of the 26 studies, 7 had small sample sizes, each of which featured fewer than 20 implants.
Implications for Dental Practice:
In this review, the high survival rate of implant-supported crowns is complicated by a 10% possibility of biologic complication like perimplantitis. One recent review (1) by the same authors reported a 5-year survival rate of 91.4% for cantilever bridges and 93.8% for conventional bridges, respectively. In another review (2) they conducted, the authors reported a 87.7% 50 year survival rate for resin-bonded bridges. Thus, although these numbers may overestimate the rate of success, it appears that in the short-term, implant-supported single crowns may be a viable treatment option for replacing a single missing tooth. Current treatment modalities can only be challenged if there is strong evidence that these alternative treatment modalities offer at least similar, if not improved, long-term survival rates with low complication rates.
1. Pjetursson BE, Bragger U, Lang NP, Zwahlen M. Comparison of survival and complication rates of tooth supported fixed partial dentures and implant supported fixed partial dentures and single crowns. Clinical Oral Implant Research 2007;18 (Suppl. 3):97–113
2. Pjetursson BE, Tan WC, Tan K, Brägger U, Zwahlen M, Lang NP. A systematic review of the survival and complication rates of resin-bonded bridges after an observation period of at least 5 years. Clinical Oral Implants Research 2008; 131-141